The present invention relates to semiconductor processing. More specifically, the present invention is directed to wafer support members that are substantially resistant to process gases and cleaning gases encountered during processing.
One of the primary steps in fabricating modern semiconductor devices is forming a dielectric, metal, or semiconductor layer on a semiconductor substrate. As is well known, such a layer can be deposited by chemical vapor deposition (CVD). The process of depositing layers on a semiconductor wafer (or substrate) usually involves heating the substrate and holding it a short distance from a source of a stream of process gas flowing towards the substrate. In a conventional thermal CVD process, reactive gases are supplied to the substrate surface where heat-induced chemical reactions (homogeneous or heterogeneous) take place to produce a desired film. In a plasma enhanced chemical vapor deposition (PECVD) process, controlled plasma is formed to decompose and/or energize reactive species in reactive gases to produce the desired film. In general, reaction rates in thermal and plasma processes may be controlled by controlling one or more of the following: temperature, pressure, and reactant gas flow rate.
Semiconductor device geometries have dramatically decreased in size since such devices were first introduced several decades ago. Since then, integrated circuits have generally followed the two-year/half-size rule (often called "Moore's Law") which means that the number of devices which will fit on a chip doubles every two years. Today's wafer fabrication plants are routinely producing 0.5 .mu.m and even 0.35 .mu.m feature size devices, and tomorrow's plants soon will be producing devices having even smaller feature sizes. In the quest to achieve ever smaller devices, certain issues have become of greater concern to the industry.
One such issue relates to the removal of contaminants from the processing chamber. The problem of impurities causing damage to the devices on the substrate is of particular concern with today's increasingly smaller device dimensions. During CVD processing, reactive gases released inside the processing chamber form layers such as silicon oxides or nitrides on the surface of a substrate being processed, and undesirable oxide deposition occurs elsewhere in the CVD apparatus, such as in the area between the gas mixing box and gas distribution manifold.
Build-up of surface deposits on the inside of the processing chamber surfaces may cause flakes or particles of the deposited material to fall from the surface of the chamber onto the substrate being processed, potentially causing defects. To avoid this problem, the inside surfaces of the processing chamber are typically cleaned by etching (e.g. plasma cleaning) their surfaces with fluorine gas to remove the dielectric material deposited by the deposition gas. Bare aluminum surfaces inside the chamber are subject to fluorine gas attack which results in unwanted aluminum fluoride (AlF) film growth. To remove the film growth, the susceptor or pedestal surface is often scraped after fluorine gas cleaning. If the suspector or pedestal is not cleaned, the aluminum fluoride film is susceptible to cracking and peeling which may cause additional particle contamination.
As would be expected, cleaning interferes with processing throughput. To reduce exposure and limit downtime from periodic chamber cleaning, it is desirable to provide multiple deposition and cleaning capabilities in a single chamber with a simplified design to minimize the time consumed for different types of chamber processes. With growing pressures on manufacturers to improve processing quality and overall efficiency, eliminating the total down-time in a multiple-step process without compromising the quality of the wafers has become increasingly important for saving both time and money. To achieve such a chamber, the components used for such a chamber would preferably be resistant to etching from cleaning gases and deposition by process gases.
In light of the above, improved methods, systems and apparatus are desired for high quality, efficient, deposition and cleaning. In particular, the desired system should allow for multiple processing and cleaning steps to occur within the same chamber without degradation in performance resulting from deposition or reaction with process or cleaning gases. Elements of the system are desirably resistant to corrosion and deposition from deposition and cleaning processes.